On Tuesday, a Ukrainian Sukhoi Su-27 fighter jet crashed during a joint NATO-Ukrainian military exercise, claiming the lives of both pilots. Although their identities have not yet been released, earlier reports suggest that one of the killed pilots was an American Air National Guard officer.

While information is still limited, the accident presumably took place during flight operations in support of NATO’s Clear Sky 2018 exercises. The crash was reported first on social media by Ukrainian military officials before being picked up by local news outlets.

“Today, around 17.00 local time [14:00 GMT], a Su-27 plane crashed near the village of Ulaniv [between the towns of Berdychiv and Khmil’nyk] during a combat training flight. Search and rescue activities are being carried out,” the Ukrainian press service said on Facebook.

“We regret to inform that, according to the search and rescue team, the bodies of two pilots have been found: one is a soldier of the Air Force of the Armed Forces of Ukraine, while another one is a soldier of the Air Forces of the U.S. National Guard.”